Solvent fixing process

ABSTRACT

A PROCESS FOR FIXING TONER IMAGES WITH A SOLVENT WHICH COMPRISES CONTACTING A FILM OF A SOLVENT FORMED ON THE SURFACE OF A GROUNDED CONDUCTIVE ROLLER WITH THE FRONT SURFACE OF A SUPPORT HAVING THEREON TONER IMAGES WHILE APPLYING TO THE BACK SIDE OF THE SUPPORT A CORONA DISCHARGE OF A POLARITY TO THE CHARGE OF THE TONER IMAGES TO THEREBY FIX THE TONER IMAGES ON THE SUPPORT, SAID SOLVENT BEING CAPABLE OF FIXING SAID TONER IMAGE AND BEING A NON-CONDUCTIVE AND NON-POLAR LIQUID.

June 19, 1973 Kolcl-u TAK|GucH| 3,740,249

SOLVENT FIXING PROCESS Filed OGL. l, 1971 LFJNS Y JPY/7 HG. I

United States Patent O U.S. Cl. 117-21 6 Claims ABSTRACT F THEDISCLOSURE A process for fixing toner images with a solvent whichcomprises contacting a film of a solvent formed on the surface of agrounded conductive roller with the front surface of a support havingthereon toner images while applying to the back side of the support acorona discharge of a polarity opposite to the charge of the tonerimages to thereby fix the toner images on the support, said solventbeing capable of fixing said toner image and being a non-conductive andnon-polar liquid.

FIELD OF THE INVENTION The present invention relates to a novel processof fixing a toner image onto the surface of a support and moreparticularly, the invention relates to a process of fixing a toner imageformed loosely on a xerographic plate, an electrostatic recording paperor on a transfer sheet electrostatically by using a solvent.

BACKGROUND OF THE INVENTION Hitherto, a toner image formed on a supportwas fixed in electrophotography by one of the following two methods. Onemethod is the use of heat and the second method is the use of solvent.

The first method is unacceptable because of faults such that the powerconsumed in the fixing by heating is great and there is a danger of fireand the practice of the continuous heating gives harmful influences onthe photoconductive layer. In spite of such faults, the xing method byheating has generally been adopted more favorably than the fixing methodby solvent because the solvent fixing method has many faults such thatin the so-called solvent-Vapor fixing method of condensing the vapor ofsolvent on the surface bearing thereon a toner image, there is thenecessity of a long period of time in the condensation of the solventvapor, which makes it difficult to speed up the fixing and makes thecontrol and maintenance of vapor difficult. The solvent iiixing methodhas also faults, such that in the method of conducting the solventfixing by contacting a back surface of the toner image-bearing sheetdirectly to a metallic roller rotated in a solvent bath with acontrolled speed the whole sheet is impregnated with the solvent fromthe back side thereof, which requires a large quantity of solvent andthe sheet is withdrawn from the fixing system in a wet state, whichrequires an additional drying step.

Therefore, an object of this invention is to provide a novel process offixing a toner image formed on a support with a solvent with aconsiderable reduction in consumption and release of solvent as comparedwith conventional solvent fixing methods. In the specification of thisinvention, the term support means a photosensitive paper or a web sheetof electrostatic recording paper each having a toner image thereon or aweb sheet to which a toner image formed on a photosensitive plate hasbeen transferred.

3,740,249 Patented June 19, 1973 ice BRIEF DESCRIPTION OF THE DRAWINGSNow, the principle of this invention will be explained by referring tothe drawings, in which:

FIG. l is a cross-sectional view showing the typical mechanism of theprocess of this invention; and

FIG. 2 is a cross-sectional view showing a modification of the processof this invention.

DETAILED DESCRIPTION OF THE INVENTION In FIG. 1, a conductive roller 1which has been grounded, is rotated by means of a motor (not shown). As01- vent 2 placed in a solvent tank 3i is a solvent capable of directlyfusing a toner image, a solvent containing a binder, or a solventcontaining a plasticizer. That is to say, a liquid used in aconventional fixing method of toner images by solvent, may be used inthis invention. The solvent is restricted in electric conductivity tosome extent by the reasons shown below. A roller 4 is immersed partiallyin the solvent and supplies the solvent onto a roller 5 in an amountcontrolled by a control blade 6. The roller S transfers the solvent thussupplied onto the surface of the conductive roller 1 to form a thin filmof the solvent on the conductive roller 1. Adjacent to the roller 1 isdisposed a cleaner 7 for cleaning away the toner offset on the roller 1.A support having formed thereon toner image 9, is supplied to thesolvent fixing system and withdrawn therefrom with fixed toner images 10by solvent. Under the roller 1 is disposed a corona discharging device11.

By the mechanism mentioned above, a solvent is supplied from the solventtank 3 in a suitably controlled amount and the film of the solvent isformed on the surface of the roller 1. The conductive roller 1 iscontacted with the surface of the sheet 8 bearing the toner images viacorona discharging. The polarity of the corona discharging is soselected that it is opposite to the charge of the toner images 9 formedelectrophotographically on the support. By this process, the tonerimages are brought into contact with the solvent film. Accordingly, thetoner images are fixed with a smaller amount of solvent than that in theconventional method and because the amount of the solvent required forthe fixing of toner images is less, the support having the fixed tonerimage withdrawn from the roller 1 is in an almost dry state and hence,requires almost no drying step.

Also by utilizing corona discharging, the sheet 8 is closely broughtinto contact with the solvent film on the conductive roller 1 to provideuniform fixing and additionally, because the polarity of the coronadischarging is opposite to the charge of the toner image, the tonerimages are attracted strongly t0 the support by the electrostaticattraction forces to reduce the offset of the toner onto the roller 1and also thereby reduces the disturbance of the toner images by solvent.As will be understood from the aforesaid mechanism, the evaporation ofthe solvent at the stoppage of the above fixing system is prevented bystopping the rotation of the roller 4 and closing the solvent tank 3.

Another embodiment of this invention is shown in FIG. 2. By thisembodiment, the solvent is supplied to the conductive roller 12 by meansof :a solvent supplying material 20, such as felt in place of the roller5 in FIG. 1. That is to say, the solvent supplied to the solvent supplymaterial 20 by means of a rotary roller 15 from a solvent tank, iscarried onto the conductive roller 12 by a capillary phenomena to form athin film of the solvent on the surface of the conductive roller 12.

In this case, a load 21 is used for forming a uniform ilm on the roller.Also, the load acts as a cleaner for the conductive roller 12 togetherwith the solvent supply member. The fixing of the toner images 17 on thesupport 16 is conducted by the same manner as mentioned in relation withthe embodiment shown in FIG. 1. 13 is, of course, the solvent in thesolvent tank 14, 18 is the xed toner image, and 19 is the coronadischarging device.

As another embodiment of this invention it is possible to pass thesupport having toner images between the conductive roller and a rollerto which an opposite bias has been applied in place of applying oppositecorona discharging to the charge of the toner images by means of thecorona discharging device in the embodiments shown in FIG. l and FIG. 2.In this case, the offsetting of toner on the conductive roller may beprevented but a solvent is accumulated between the two rollers and whenthe support is passed between the rollers, the top portions of the sheetare supplied with an excessive amount of solvent to disturb the tonerimages. For preventing such diiculty a mechanism of narrowing the spacebetween the two rollers only during the passage of the sheet is used.

As mentioned above, the solvent used in this invention must not have aproperty of losing the charge of the toner images. Accordingly, a liquidhaving a high electric conductivity or having a polarity cannot be used.As the solvents satisfying the above conditions, liquids usually use'das dispersing mediums for liquid developers in electrophotography aredesirably used.

EXAMPLE l The fixing system shown in FIG. l was used. As the conductiveroller 1, an aluminum roller having a diameter of 38 mm. was used. Thediameter of the roller 4 was 28 mm., and the diameter of the roller was18 mm. The solvent used was l,l,1trichloroethane. A Wire of 0.1 mm., indiameter was placed as an experimental corona discharging device with adistance of 14 mm. from the surface of the roller 1 and an electricpotential of 6 kv. was applied to the wire.

The rollers, 1, 4 and 5 were rotated in the direction of the arrow at aline speed of 70 mur/sec. and when a paper sheet having unxed tonerimages formed by toners charged negatively was passed through the`fixing system, good ixed toner images were obtained. The paper sheethaving the iiXed toner images was also obtained in an almost dry state`and no offset of toner was observed on the roller.

Also, when trichloroethylene was used as the solvent for xing in thesame -xing system as above, almost the same good xing was achieved.Moreover, when a sheet having toner images positively charged was usedand an electric potential of -6 kv. was applied to the coronadischarging device, almost similar good Ifixing was achieved.

EXAMPLE 2 The iixing system as shown in FIG. 2 was used. As theconductor roller 12 an aluminum roller having a diamter of .38 mm. wasused and the diameter of the roller 15 was 2l mm. Also, a felt of 4 mm.in thickness was used as the ysolvent supply material 20. By conductingthe same fixing procedure as in Example l using the same coronadischarging device and l,l,ltrichloroethane or trichloroethylene as thesolvent, a good fixing was obtained. For the toner images positivelycharged, an electric potential of -6 kv. was applied and for the tonerimages negatively charged, an electric potential of +6 kv. was appliedto the corona discharging device. The line speed of the roller 1 was 70mm./ sec.

What is claimed is:

1. A process for fixing toner images with a solvent which comprisescontacting a ilm of a solvent formed on the surface of a groundedconductive roller with the front ysurface of a support having thereontoner images while applying to the back side of the support a coronadischarge of a polarity opposite to the charge of the toner images tothereby fix the toner images on the support, said solvent being capableof iixing said toner images and being a non-conductive and non-polarliquid.

2. The process as set forth in claim 1 wherein the solvent i-s suppliedonto the surface of said conductive roller by means of solvent supplyrollers.

3. The process as set forth in claim 1 wherein said solvent is suppliedto said conductive roller by a solvent supply fibrous material.

4. The process as set forth in claim 3 wherein said ibrous materialcomprises felt.

5. The process as set forth in claim 1 wherein said solvent istrichloroethane or trichloroethylene.

6. The process as set forth .in claim 1 wherein said solvent comprisesan electrophotographic liquid developer dispersing medium.

References Cited UNITED STATES PATENTS 2,684,301 7/1954 Mayo 117-21FOREIGN PATENTS 267,804 7/1964 Australia 1l7-l7.5

MURRAY KATZ, Primary Examiner M. S. FOCLEOUS, Assistant Examiner U.S.Cl. X.R. 1l7-l7.5;96-1 R

